The latest generation of high infrared lasers and

The new generation of high infrared lasers and their scientific research applications

thin slice semiconductor pumped solid-state lasers are considered to be one of the most famous developments in laser technology in recent years. Based on a revolutionary solid-state laser design concept, it has become a right-hand man in scientific research and industrial processing in recent years, and has entered the stage of mass production in recent years. Thin slice solid-state lasers can output high power (continuous or pulsed) and have very good beam quality

yb:yag laser crystal, as a special laser working material, not only has excellent physical properties and stable chemical properties of YAG laser matrix material itself, but also has good laser working properties. The laser wavelength is 1030nm, the peak absorption wavelength is around 940nm, and the absorption bandwidth is very wide（ 18nm@940nm ）, long fluorescence lifetime (0.95ms) and high quantum efficiency (91%). At the same semiconductor pump power, yb:yag pump heat generation is 1/3 of nd:yag. It can be easily pumped by a reliable InGaAs semiconductor laser. It is a new laser material with high average power and high beam quality, which is suitable for LD pumping and emits about 1um wavelength. In addition, because the second harmonic generation 5. The main bearing of the dynamometer does not allow refueling is 515nm, which is close to the wavelength of the Ar ion laser of 514.5nm, making it possible to replace a large number of existing argon ion lasers, it has attracted more and more attention in the laser field

the thin-film solid-state laser technology invented by Dr. adolfgiesen of the University of Stuttgart in Germany and his research team has far better performance than the nd:yag solid-state laser designed with traditional rod crystals. As the patent is funded by the German government, it can only be licensed to German laser companies. This is the reason why only German laser companies can produce thin-film solid-state lasers at present. ELS company of Germany is the first and the only manufacturer of high-power sheet type single frequency continuous solid-state lasers in the world. The versadisk laser produced by it won the photonicsexcellenceaward2003 award, and it was the only solid-state laser in the world that won this award. Therefore, versadisk is being accepted by more and more scientific research users, all thanks to its unique design concept and distinctive performance. Moreover, versadisk515 has further expanded the application field of high-power solid-state green laser, breaking the situation that the market has been occupied by American laser companies in the past

1. principle

the appellation of sheet laser comes from the fact that its crystal shape is sheet type, its thickness is usually 200 microns, and its diameter is 10mm. It is pumped by a semiconductor laser from the front surface of the crystal, which is similar to the commonly used end pump technology. The whole thin crystal is bonded to the heat sink, so the cooling efficiency of the crystal is very high with the specified non proportional elongation stress Rp0.2 (MPA) (Fig. 1). Because the thickness of the crystal is very thin, every time the pump light of the semiconductor laser passes through the laser crystal, only a part of the pump light is absorbed by it, but the radius of curvature of the notch should be made to be less than the critical value. In order to improve its pumping efficiency, a paraboloid mirror is placed in front of it, so that the unabsorbed pump light passes through the crystal many times to improve the dogma pumping efficiency of law rather than paper. The general number of times is 32, Thus, strong laser radiation is generated

2. Comparison with traditional rod-shaped nd:yag solid-state lasers:

yb:yag, as a quasi three-level crystal, is more suitable for semiconductor laser pumping than traditional nd:yag crystal. Compared with nd:yag crystal, its advantages are as follows:

· it has low quantum loss, small thermal load (91% quantum efficiency), and very small thermal lens effect, which can be almost ignored

· it has a wide absorption bandwidth (18NM), so the temperature control accuracy of the pump LD is low

· the upper level fluorescence has a long lifetime (1ms), which is conducive to energy storage

· wide emission linewidth enables tuning output

· the laser emission cross section is small (conducive to high-energy storage)

yb: the heat conduction and temperature gradient of YAG crystal are mainly along the axis, so that the temperature distribution of the crystal is very uniform and the wavefront deformation is very small. This advanced resonator design makes the efficiency of heat conduction from yb:yag crystal to heat sink very high, and the direction of heat conduction is parallel to the direction of laser beam propagation (i.e. axial), so the radial temperature gradient is very small, thus avoiding the solid limitations of traditional rod crystal lasers, such as thermal lens effect, laser crystal deformation, birefringence effect, etc. at high power. Therefore, sheet solid-state lasers can easily obtain very high output power (maximum 100W) without affecting its excellent optical performance. Generally, they have high-power laser beams (M2 1.1) with near Gaussian distribution. This is the biggest difference between it and the traditional rod nd:yag solid-state laser, because the traditional rod nd:yag solid-state laser either has high power or has good beam quality, but it can't have it at the same time

3. powerful optical platform:

versadisk of ELS company in Germany is not just a laser, it is actually a powerful optical platform. Modular design brings you flexible configuration and strong scalability (Figure 3). Users can choose the most appropriate configuration according to their own research work, or choose a general configuration to meet most common applications. Versadisk cavity structure has a very high degree of freedom. Users can buy only one laser and get infrared (fundamental frequency), green light (frequency doubling) or dual wavelength (infrared and green light) output at the same time. They can also insert etalon, Brewster window and birefringent filter into the cavity to realize many functions that traditional rod solid-state lasers cannot achieve, such as single frequency, linear polarization and wavelength tunability